The show chronicled the weekly adventures of the Cartwright family, headed by the thrice-widowed patriarch Ben Cartwright (played by Lorne Greene). He had three sons, each by a different wife: the eldest was the urbane architect Adam Cartwright (played by Pernell Roberts) who built the ranch house; the second was the warm and lovable giant Eric, better known by his nickname "Hoss" (played by Dan Blocker); and the youngest was the hotheaded and impetuous Joseph or "Little Joe" (played by Michael Landon). The family's cook was the Chinese immigrant Hop Sing (played by Victor Sen Yung). Bonanza was considered an atypical western for its time, as the core of the storylines dealt less about the range but more with Ben and his three dissimilar sons, how they cared for one another, their neighbors and just causes.
The family lived on a thousand-square-mile  ranch called Ponderosa on the shore of Lake Tahoe in Nevada. The massive size of the Cartwright's land was quietly revised to "half a million acres" on Lorne Greene's 1964 song, "Saga of the Ponderosa" ("Bonanza" set liner notes, Bear Family Records, disk 1). The ranch name refers to the Ponderosa Pine, common in the West. The nearest town to the Ponderosa was Virginia City, where the Cartwrights would go to converse with Sheriff Roy Coffee (played by veteran actor Ray Teal), or his deputy Clem Foster (Bing Russell). Greene, Roberts, Blocker, and Landon were billed equally. The opening credits would alternate the order among the four stars. As the series advanced, writers began to showcase one or two Cartwrights in each episode, while the others would be seen briefly in the prologue and epilogue. Not only did this provide for more thorough character development, it also gave all four actors more free time.
Originally, the Cartwrights tended to be depicted as put-off by outsiders. Lorne Greene, however, objected to this, pointing out that as the area's largest timber and livestock producer, the family should be less clannish. The producers agreed with this observation and changed the Cartwrights to be more amiable.
In the fall of 1972, Bonanza was moved to Tuesday nights opposite the All In The Family spinoff, Maude. The scheduling change, as well as Dan Blocker's death several months earlier, resulted in plunging ratings for the show. David Canary returned to his former role of Candy (to offset Hoss' absence), and a new character named Griff King (played by Tim Matheson) was added to lure younger viewers. Griff, in prison for nearly killing his abusive stepfather, was paroled into Ben's custody and got a job as a ranch hand. Several episodes were built around his character, one that Matheson never had a chance to fully develop before the show's sudden cancellation in January 1973. Many fans felt that the Hoss character was essential, as he was a nurturing, empathetic soul who rounded-out the all-male cast.